The invention relates generally to internal combustion engines and more particularly to two-stroke internal combustion engines. Still more particularly, the invention relates to multi-cylinder two-stroke internal combustion engines including two-cylinders which operate in an out-of-phase relation to each other.
In conventional two-stroke engines, the engine crankcase is used to pump the engine working fluid (primarily air) from the atmosphere and to purge (scavenge) the cylinder of combustion exhaust components and to replace them with air for the next combustion cycle.
Engine output is typically controlled by throttling air before it passes through a one-way check valve or reed valve before it is inducted into the engine crankcase. In the case of high output engines, one throttle valve is typically provided to control the flow of air through each reed valve into each crankcase. The use of a separate throttle for each cylinder as well as the mechanical linkage needed to operate multiple throttles increases the cost and complexity of an otherwise simple and inexpensive two stroke engine.